1. Field of the Invention
The present invention relates to a reproducing apparatus and a reproducing method, and more particularly, to an interpolating technique related to a specific reproduction image.
2. Related Background Art
There is known a digital VTR for encoding an image signal and recording and reproducing the encoded image signal on and from a magnetic tape. Also, there is known a VTR that produces high-speed reproduction (specific reproduction) data such as search reproduction in addition to a normal reproduction image signal that is subjected to moving picture experts group (MPEG) encoding to record image data in a predetermined area on a magnetic tape.
As an example, a description will be given in which an image signal of 1440×1080i is encoded, and recorded on the magnetic tape. The effective pixels of the image signal to be encoded are 1440 samples in the horizontal direction and 1080 lines in the vertical direction with respect to a luminance signal Y, and 720 samples in the horizontal direction and 540 lines in the vertical direction with respect to color difference signals Cb and Cr, respectively.
The signal is divided into macro blocks (MB) to provide 90 macro blocks in the horizontal direction and 68 macro blocks in the vertical direction as shown in FIG. 1, and encoded. The macro blocks of the luminance signal is made up of four DCT blocks, and each of the color difference signals Cr and Cb includes macro blocks each of which is made up of one DCT block. Also, a DC component is extracted from the DCT block of an I picture that is made up of an intra frame, thereby producing specific reproduction data (for example, refer to Japanese Patent Application Laid-Open No. 2001-298706).
In this situation, the data of the extracted DC component is converted into 6 bits with respect to the luminance signal Y and converted into 5 bits with respect to the color difference signals Cb and Cr, respectively. As a result, the specific reproduction data can be produced with a fixed length of (6×4+5×2)=34 bits per one macro block and (90×68×34)=208080 bits per one frame.
Also, the specific reproduction data is reproduced from the I picture. For example, when one group of pictures (GOP) is made up of 15 frames and B pictures arranged between an I-P picture and a P-P picture are made up of 3 frames, as shown in FIG. 2, the I picture is encoded every 15 frames, so the specific reproduction image is produced every 15 main image frames.
Also, as shown in Japanese Patent Application Laid-Open No. 2002-209179, there is proposed an information recording device using a method in which the above-mentioned specific reproduction data is divided into a group of luminance signal Y0 and color difference signals Cb and Cr, and a group of luminance signals Y1, Y2, and Y3 in the macro block, the respective groups are packetized with fixed lengths, and thereafter those packet signals are subjected to an error correction encoding process and recorded on the magnetic tape, independently, thereby making it possible to readily and roughly display an entire screen even in the case where there is dropout specific reproduction data.
FIGS. 3A and 3B show dropouts of respective packets in the case where the specific reproduction data is divided into a group of luminance signal Y0 and color difference signals Cb and Cr, and a group of luminance signals Y1, Y2, and Y3 in the macro block, the respective groups are packetized with fixed lengths, and thereafter those packet signals are subjected to an error correction encoding process and recorded. FIG. 3A shows a case of packet dropout of luminance signal Y0 and color difference signals Cb and Cr. FIG. 3B shows a case of packet dropout of luminance signals Y1, Y2, and Y3.
As described above, the specific reproduction data is divided into the group of the luminance signal Y0 and the color difference signals Cb and Cr, and the group of the luminance signals Y1, Y2, and Y3 in the macro block, and those signals are subjected to the error correction encoding process and recorded, independently. At the time of reproduction, when there exists an error in the reproduction data due to some factor and there occurs dropout of specific reproduction data, the luminance data Y0 and the luminance data Y1, Y2, and Y3 in the macro block drop out, individually.
The respective dropout luminance data corresponds to an area of 8×8 pixels in the reproduction image. Therefore, in the case where the dropout area is interpolated by an image of another block within the same frame, there is the possibility that an asperity pattern is highly visible in the reproduced image.
Also, as the interpolating method, there has been proposed the use of image data of a frame that has already been reproduced. However, because the specific reproduction data is produced from the I picture, it is general that the specific reproduced image is produced every plural frames of the main image. For example, as shown in FIG. 2, in the case where the one GOP is made up of 15 frames, an image before one frame in the specific reproduction data corresponds to an image before 15 frames in terms of the normal reproduction main image. For that reason, in the case where the dropout data is interpolated by using the image data of the frame that has been reproduced immediately before the subject frame, a difference from the surrounding blocks becomes large, and the interpolation block is highly visible.
In this way, there has been required an interpolating method that takes dropout of the specific reproduction data on the packet base into consideration.